The pineal gland exerts a profound effect upon gonadal function in several vertebrate species. Melatonin is an indole amine synthesized exclusively in the pineal gland, and appears to be the major compound secreted which influences gonadal function. Melatonin is synthesized from serotonin by N-acetyl transferase (NAT) which converts it to N- acetylserotonin. A second enzyme, Hydroxyindole-o-methyl transferase (HIOMT), o-methylates the N-acetyl-serotonin and converts it to melatonin. Both enzymes have been used as indices of pineal activity. In rats, the pineal inhibits gonadal activity. Light perception inhibits pineal activity while constant darkness is stimulatory. Upon exposure to light, norepinephrine is released into the pineal from sympathetic nerves, resulting in an activation of pineal adenyl cyclase activity. The resulting cyclic AMP has been reported to stimulate melatonin synthesis. Estrogens inhibit this response of adenyl cyclase to norepinephrine stimulation. In Coturnix quail, the pineal stimulates gonadal maturation. This response is sensitive to photoperiod, with exposure to long photoperiods (16L:8D) resulting in increased HIOMT activity and melatonin synthesis. During development, the HIOMT activity declines near the onset of oviposition. Ornithine decarboxylase (ODC) is an enzyme which is in high levels in many tissues undergoing rapid growth or secretory processes. It has been demonstrated to increase dramatically in several endocrine tissues upon hormonal stimulation. We propose to investigate the mechanisms which regulate pineal function in Coturnix by determining the effects of photoperiodicity and sex steroids upon pineal adenyl cyclase, NAT, HIOMT and ODC activities. We propose to determine whether ovarian sex steroids exert a negative feedback influence upon these systems, resulting in decreased melatonin synthesis near the onset of oviposition.